It would be desirable for electrical utilities and other entities which use electrical transformers to have the ability at low cost to monitor the condition of their electrical transformers while such systems are either on-line or when such systems are off-line immediately following a fault condition. The fault condition may be dependent or independent of the transformer being monitored. A variety of techniques have been employed to monitor the condition of transformers in order to evaluate whether or when maintenance should be performed. However, to date such systems lack the ability to continuously monitor the deterioration of liquid insulation (e.g., transformer oil) within electrical transformers at low cost and without efficiency loss.
Currently, there are at least 40 liquid insulation tests for analyzing the condition of electrical transformer oil. These tests typically require extraction of a transformer oil sample from the transformer, followed by analysis (typically in a laboratory) of the extracted oil sample. Some of the analysis techniques include introducing an indicator that reacts with particular substances in the liquid insulation. Since these analysis techniques leave the liquid insulation contaminated with a substance that is not normally in the transformer, the contamination of the fluid makes these test methods unsuitable for an on-line monitoring system.
One on-line system currently in use for monitoring electrical transformers is a gas analysis system. This system monitors specific gases involved in the breakdown of liquid insulation within a transformer. Because gas analysis systems monitor the presence/absence of only a specific limited number of gases, such systems lack the ability to detect substances for which they have not been calibrated. Another deficiency in gas analysis systems is their reliance on filters which separate gases from the liquid insulation. As liquid insulation becomes saturated with particulates during degradation of the insulation, such filters become clogged with these particulates.
Another on-line system currently in use for monitoring electrical transformers uses spectroscopy. This system automatically withdraws a fluid sample from the transformer fluid circuit and performs spectral analysis on the sample. This system requires at least 30 minutes between each sample collection. It is still advisable to perform a more complete gas concentration analysis test after this spectral analysis test or any other on-line test.
Gas analysis tests performed off-line test for Hydrogen, Ethane, Ethylene, Acetylene, Carbon Monoxide and Carbon Dioxide. One interpretation of an abundance of acetylene would indicate an electrical fault. Ethylene is produced by thermal degradation. By interpreting the gas analysis results it may be determined what has occurred in a transformer. One down side of this test is the fact that the transformer must be taken off-line for an oil sample to be withdrawn.
A further method for determining the condition of a transformer is direct visual inspection of the internal components. This method of course requires that the system be taken out of service and opened.
It is therefore an object of the present invention to provide a low cost system for analyzing changes in the optical characteristics of fluids which may be correlated directly to the concentration of chemical constituents or contaminants.
It is a further object of the present invention to provide a system which operates on-line simultaneously while the transformer is either in operation or immediately after a fault condition.
It is a still further object of the present invention to provide a low cost system which can be easily fitted or retrofitted onto existed liquid type electrical transformers in order to continuously analyze the condition of liquid insulation within such transformers.
It is a still further object of the present invention to provide a low cost system for monitoring transformer fluid, which system to continues to function even after the transformer oil becomes a solvent or saturated with particulates.
It is a still further object of the present invention to provide a system which indicates when increased amounts of paper insulation and water particulates are present in transformer oil. It is a still further object to provide such indications independently of external computer processing and telecommunication links.
It is a still further object of the present invention is to provide a system that supplies information to system operators and power plant managers to aid in determining when to place a piece of equipment back in operation following a fault without further test analysis.
These and other objects and advantages of the invention will become more fully apparent from the description and claims which follow or may be learned by the practice of the invention.